Ray Optics

INTRODUCTION

In optics, a ray is an idealized narrow beam of light. Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of ray tracing.

REFLECTION OF LIGHTREFLECTION OF LIGHT

It is a phenomenon of change in the It is a phenomenon of change in the path of light without any change in path of light without any change in medium.medium.

The reflection of The reflection of Mount Hood in Mount Hood in Trillium Lake.Trillium Lake.

LAWS OF REFLECTION

The laws of reflection are as follows:The incident ray, the reflected ray and the

normal to the reflection surface at the point of the incidence lie in the same plane.

The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.

Reflection through Reflection through Spherical MirrorsSpherical Mirrors

Concave Mirror Convex Mirror

REFRACTION OF LIGHT It is the phenomenon of change of light,

when it goes from one medium to another.

Refraction is described by Snell’s law, which states that the angle of incidence is related to the angle of refraction by

where n1 and n2 are the refractive indices

sin i

sin r =

n2

n1

REAL AND APPARENT REAL AND APPARENT DEPTHSDEPTHS

A pencil in a bowl of water appears A pencil in a bowl of water appears shallower than what it actually is. This shallower than what it actually is. This is on account of refraction of light.is on account of refraction of light.

Real depth

Apparent depth= a nw

Refraction through LensesRefraction through Lenses

Concave Lens Convex Lens

LensesLenses It is a portion of a transparent refracting It is a portion of a transparent refracting

medium bound by two spherical surface medium bound by two spherical surface or one spherical and other plane surface.or one spherical and other plane surface.

Biconvex lensBiconvex lens Plano-convex lensPlano-convex lens Biconcave lensBiconcave lens Plano-concave LensPlano-concave Lens

Types of Lenses:

PRISMPRISM A prism is a portion A prism is a portion

of a transparent of a transparent medium bounded medium bounded by two plane faces by two plane faces inclined to each inclined to each other at a suitable other at a suitable angle.angle.

DISPERSION OF LIGHTDISPERSION OF LIGHT

It is a It is a phenomenon of phenomenon of splitting of a splitting of a beam of white beam of white light into its light into its constituent constituent colours on colours on passing through a passing through a prism.prism.

White

Light

OPTICAL INSTUMENTSOPTICAL INSTUMENTS

The eye is far more The eye is far more delicate and perfect delicate and perfect than the finest than the finest photographic camera photographic camera designed so far. The designed so far. The essential parts of the essential parts of the eye are shown.eye are shown.

Eye:

Defects of Vision

Myopia (Short Sightedness) Hypermetropia (Long

Sightedness) Presbyopia (Old Sight) Astigmatism Phorias

Simple MicroscopeSimple Microscope

It is used for observing magnified It is used for observing magnified images of tiny objects.images of tiny objects.

The course of raysThe course of rays through a simplethrough a simple microscope ismicroscope is shown. F,F are theshown. F,F are the principle foci and C isprinciple foci and C is the optical centre ofthe optical centre of the convex lens.the convex lens.

Magnifying Power of Simple Microscope:

The magnifying power of Simple Microscope is defined as the ratio of the angles subtended by the image and the object on the eye.

The magnifying power is given by:

m = ( )1+d

f

Compound MicroscopeCompound Microscope

It is an optical instrument used for It is an optical instrument used for observing highly magnified images of observing highly magnified images of tiny objects.tiny objects.

It consists of twoIt consists of two

converging lenses.converging lenses. The course of raysThe course of rays

through a compoundthrough a compound

microscope is shown.microscope is shown.

Magnifying Power of Compound Microscope:

The magnifying power of Compound Microscope is defined as the ratio of the angle subtended by the final image to the angle subtended at the eye by the object.

The magnifying power is given by:

m = ( )1+d

fe

v0

u0

Astronomical TelescopeAstronomical Telescope

It is an optical instrument which is It is an optical instrument which is used for observing images of heavenly used for observing images of heavenly bodies like stars, planets etc.bodies like stars, planets etc.

The course of raysThe course of rays

when the finalwhen the final

image is formed atimage is formed at

the least distancethe least distance

of distant visionof distant vision

from the eye.from the eye.

Magnifying Power of Astronomical Telescope:

The magnifying power of Astronomical Telescope is defined as the ratio of the angle subtended by the final image to the angle subtended at the eye by the object at infinity, when seen directly.

The magnifying power is given by:

m = ( )1+fe

d

f0

fe

Thank You

Presented by :-

ABHISHEK & PAWAN

Xii – Sci

FAITH ACADEMY

2008-09